What happened today in France's presidential race

French presidential election candidate for the right-wing Les Republicains party Francois Fillon (C) reacts as a man throws flour at him on April 6, 2017 during a political rally in Strasbourg

With just 17 days left before the first round of France's presidential election, a protester blanketed scandal-plagued candidate Francois Fillon with flour, and the two frontrunners fell back slightly in the polls.

Here are three things that happened in the campaign on Thursday:

- Flour power -

At a campaign event in the eastern city of Strasbourg, a young man wearing a T-shirt emblazoned with the slogan "Students for Fillon" emptied a packet of flour on the candidate, who has been charged with abuse of public funds in a fake jobs scandal.

"I'm the target of merciless persecution," Fillon said at the rally.

Once the odds-on favourite in the race, Fillon, 63, had to overcome intense pressure to step aside after revelations in January that he had hired his wife as a parliamentary aide with little work to show for her generous pay.

Other scandals have piled up, including a revelation that Fillon accepted gifts of luxury suits from a wealthy benefactor -- which he has since returned.

Earlier Thursday, Fillon said he knew who was behind the "fake jobs" revelations.

"I have the date, the days, the people who passed on the documents," he told France Inter radio, again accusing President Francois Hollande of being behind a conspiracy to defame him.

The co-editor of the Canard Enchaine newspaper, which broke the story, laughed off the accusations that documents had been handed to its reporters.

"As an editor I would love to find an envelope stuffed with revelations like these every morning!" Louis-Marie Horeau told AFP.

- Is the race tightening? -

A new poll of voter intentions by the Elabe survey group showed independent centrist Emmanuel Macron and far-right leader Marine Le Pen still out in front before the first round on April 23, but both lost some momentum.

Macron was at 23.5 percent, down two points over a week, and at the same level as Le Pen, who lost half a point.

Scandal-hit Republicans party candidate Fillon was projected at 19 percent, up a point, while hard-left candidate Jean-Luc Melenchon continued his late surge, gaining two points to 17 percent.

Melenchon meanwhile topped Elabe's latest popularity survey, with 51 percent of respondents saying they had a positive view of him.

Macron is second with a 44 percent standing, while Fillon scored 23 percent.